What is comma operator in c language and examples

The comma operator means that in C language, multiple expressions can be separated by commas. The values ​​of the expressions separated by commas are settled separately, but the value of the entire expression is the value of the last expression. .

The comma operator means that in C language, multiple expressions can be separated by commas, where the values ​​of expressions separated by commas are resolves, but the value of the entire expression is the value of the last expression.

Example:

int a1,a2,b=2,c=7,d=5; // Line 1

a1=( b,c--,d 3); // Line 2

a2= b,c--,d 3; // Line 3

For the code assigning value to a1, there are three expressions, separated by commas, so the final value should be the value of the last expression, which is the value of (d 3), which is 8, So the value of a1 is 8.

There are also three expressions for the code that assigns a value to a2. The three expressions at this time are a2= b, c--, d 3, (this is because the assignment operator takes precedence over the comma operator level) Although the value of the final expression is also 8, b=4 (when the second line of code is completed, b=3, that is, when the third line of code is run, the value of b is 4 ), so a2=4.

Note: The associativity of comma operation is from left to right. After completion, the value of the entire expression is the value of the last expression.

Example: int a[2],x=2,y=5;

##a[0]=(x 3,y ,x );Then the final result is:a[0]=2 x=3 y=6;

Why a[0]=2: Because (x) is after the operation Then add

a[1]=(x,x 3,x 7);Then the final result is:a[1]=10,x=3

Another example of associativity:

int i=24;

int n = (i ,i ,i ,i ); // n == 27

Because the associativity of the comma operator is from left to right, the four i's will be run in sequence, but the last i will be calculated after the assignment. , so 27 is returned in the end.

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